1. Field of the Invention
The present invention relates to improvements in the ink supply and circulation system of continuous ink jet printers and more specifically to ink cartridge constructions and cooperative structure of such printer apparatus that facilitate user replacement of ink supply/return reservoirs.
2. Description of the Prior Art
In continuous ink jet printing apparatus streams of uniformly spaced ink drops are created by imposing predetermined vibrations upon liquid ink filaments issuing from an orifice plate. The filaments are formed by supplying ink under pressure to a print head cavity that is in communication with the orifice plate. Information is imparted to the droplet streams by selective non-charging or charging and deflection of droplets. A portion of the droplets pass to the recording medium but there are a substantial number of non-printing droplets that are intercepted by a catcher for recirculation. Often the print head cavity has an outlet other than the orifice plate (e.g. to facilitate dynamic pressure control within the cavity at start-up), and the apparatus ink supply system also circulates such ink flow. In many applications there are a variety of other fluid couplings to the ink reservoir that may be useful.
In view of the relatively complicated nature of the fluid system of continuous ink jet printing apparatus, one common approach has been to construct the ink supply/return reservoir as a permanent part of the printer. Thus all couplings between the supply/return reservoir and the various fluid lines of the printer are of a permanent nature and ink is added to the reservoir, when needed, e.g. by pouring from a bulk supply. This approach is perfectly acceptable for printer applications wherein dedicated operators perform the machine maintenance. However, in office applications, where the maintenance is performed by less-trained users and ink spillage is more objectionable, this approach is not desirable. It therefore is advantageous to provide ink for such office-environment printers in disposable cartridges that are simply insertable and removable by relatively inexperienced operators.
Such a disposable cartridge approach has been used in more simple ink jet printers, e.g. drop on demand printers, as well as in electrographic printing apparatus for replenishing toner. One typical prior art implementation of the cartridge approach provides a penetratable or rupturable closure portion on the cartridge and cooperative probes within the apparatus which penetrate or open the cartridge when it is inserted by the operator. While this implementation is useful for simplifying the operator involvement, it is not always adequate from the ink spillage view-point. Further, in more sophisticated continuous ink jet printing apparatus, there are often a plurality of predetermined connections that must be reliably and accurately effected between the ink circulation system of the apparatus and any replaceable supply/return reservoir.